<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
<div id="app">
<input v-model="toDoMsg"></input>
<p>{{toDoMsg}}</p>
<button @click="appendMsgToList">添加</button>
<p v-for="(item,index) in toDoList":key="index" >
    <span>{{item}}</span>
</p>
</div>
<script src="https://cdn.jsdelivr.net/npm/vue@2"></script>  
    <script>
        new Vue({
            el:'#app',
            data:{
               toDoMsg:'',
               toDoList:[]
            },
        methods:{
      appendMsgToList(){
      if(this.toDoMsg){
          this.toDoList.push(this.toDoMsg);
      }
  }
        },
    })
    </script>
</body>
</html>